The appearance of structural modifications in proteins is a well documented symptom of biological aging which can be used to study the latter process. The major goal of this project is to collect data on age-sensitive measures of protein status in a cohort of 600 UM-HET3 mice to provide information about map positions on loci that influence protein function, and to test for suggestive correlations between protein status and other structural and functional indices of aging rate. The project focuses on two proteins, the glycolytic enzyme phosphoglycerate kinase (PGK) and the eye lens proteins, in particular the chaperone-protein alpha-crystallin. These two protein systems have very different structures, biological and physical characteristics, but both are altered by aging in mice. The specific aims of Project 4 include: 91) To examine thermal inactivation rate and immunotitration data for PGK in brain, heart and liver in the 600 mice of Population 1. Thermal inactivation rate decline sup to 7-fold between 6 and 27 months in rats, while immunologically abnormal PGK appear to various ages in most tissues. (2) To quantitate the extent of modification of eye lens proteins in these 600 mice by optical techniques with sensitivity to changes in molecular weight, in structure and in spectroscopic signatures, to be applied both to intact lenses and to extracted lens proteins. (3) The same battery of tests will be performed ont he genetically selected (and control) mice in Population 2 to see in alleles that alter longevity also influence protein conformation and cross-linking. In addition to providing information about genes that may control these age-sensitive traits, our data should help to determine whether inter-animal differences in protein status might contribute to functional changes in age-sensitize tissues (bone, muscle, immune system) and whether protein functional status is likely to be regulated by oxidation and glycoxidation processes addressed in Project 5. The comparisons, which can only be made in the context of a multi- disciplinary program project, will test our hypothesis that biochemical signatures that correlate with older age will be associated with other age-sensitize phenotypes and be under over-lapping genetic control. In addition to the above listed aims, which pertain to the Program as a whole, Project 4 will also address the following project-specific issues: 1. Test whether the increased aggregation-propensity of proteins in the old eye lens is due to a reduction in the protection afforded by alpha-crystallin. 2. Search for the molecular origin of the age-related loss in alpha-crystallin's efficacy as a chaperone protein. 3. Develop and test additional experimental approaches for protein-modifications- studies, to be applied in future Program work.